Graded voltage regulation direct current power supply for electromagnetic detection emission

Abstract

The invention belongs to the field of electromagnetic detection instrument equipment, and relates to a graded voltage regulation direct-current power supply for electromagnetic detection emission, which comprises a three-phase diode rectifier bridge, an electrolytic capacitor, an H-bridge inverter, a high-frequency transformer, a high-frequency diode rectifier, a direct-current filter capacitor and the like, a three-phase alternating-current power supply is connected through a circuit breaker, three-phase alternating-current voltage of the three-phase alternating-current power supply is converted into direct-current voltage through a three-phase diode rectifier bridge, and then the direct-current voltage is output to an electrolytic capacitor to be filtered, so that voltage ripples in a direct-current link are reduced; the filtered direct-current voltage is converted into high-frequency alternating-current voltage through an H-bridge inverter; high-frequency alternating-current voltage passes through a secondary winding of the high-frequency transformer to form isolated high-frequency alternating-current voltage, the isolated high-frequency alternating-current voltage is rectified through the high-frequency diode rectifier to form direct-current rectified voltage, and then the direct-current rectified voltage is output after being filtered through the direct-current filter capacitor. The circuit can improve the control precision under the condition that the high-voltage direct-current power supply outputs low voltage.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic detection instrument equipment in geophysical detection, and relates to a graded voltage-regulated direct current power supply used for electromagnetic detection emission. Background Art

[0002] The development and utilization of mineral resources is the foundation of social and economic development. Especially in recent years, with the rapid economic development, the demand for energy minerals has been increasing, and prospecting has become an important research direction for the development of natural resources. Using geophysical detection instruments, especially electromagnetic detection instruments and equipment, to carry out deep detection is an important way to solve the shortage of energy and mineral resources. Electromagnetic detection instruments and equipment use an electrical source emission system. Through the grounding electrode and the transmitting wire, the emission current is formed, the excitation magnetic field is established, and the electromagnetic response of the target is detected to reflect the electrical characteristics of the underground medium, thereby realizing the detection of underground energy minerals and other resources. The electromagnetic detection instrument transmission system supplies power to the two grounding electrodes. Due to different geological conditions and different regional detection needs, the grounding load impedance is different, and the length of the transmitting antenna is different, resulting in different loads on the electromagnetic detection instrument transmission system, and its output voltage needs to be adjusted. In order to adapt to the grounding resistance conditions in different areas of engineering applications, the general electromagnetic transmission system DC power supply is 1500V~2000V. The closer the output voltage of the DC power supply is to the rated voltage, the better the output voltage stability is. However, in field applications, the grounding conditions are sometimes good, resulting in a small transmitter load resistance and a DC power supply output voltage of less than 100V. Or, when the instrument system is tested and calibrated before field application, the receiving system is close to the transmitting antenna and often needs to output a smaller current. In this case, the DC power supply output voltage is much smaller than the rated voltage, causing the DC power supply to work unstable.

[0003] In terms of the transmission system of electromagnetic detection instruments, the more famous instruments abroad include the TXU-30 transmitter developed by Phoenix Company of Canada [1] and the GGT-30 transmitter developed by Zonge Company of the United States [2]. The TXU-30 transmitter uses a DC power supply with an AC / DC topology structure, and achieves stable output DC voltage through PWM control; the GGT-30 transmitter increases the line voltage of 208 V 400 Hz AC power to 250 V, 500 V, 750 V or 1000 V through an adjustable transformer, and the adjustable transformer realizes rough voltage regulation. Then, the duty cycle of the SCR controlled rectifier bridge is adjusted to achieve the purpose of precise voltage regulation. The low-pass filter composed of L and C is used to filter out the voltage ripple after rectification. The duty cycle of the SCR controlled rectifier bridge is adjusted to achieve the purpose of current stabilization. In 2021, it was proposed to achieve the output of electromagnetic detection transmission voltage higher than the output through cascade rectification, and the constant current uniform control scheme of two cascade modules was studied [3]. In 2017, Huang Jiangbo et al. conducted research on the DC power supply, transmitter control and loss and heat dissipation analysis of electromagnetic detection [4-6]. Usually, the electromagnetic detection transmission system considers the system stability under rated output conditions, but lacks analysis of the full range of working conditions. Summary of the invention

[0004] In order to solve the problem of unstable operation of DC power supply when outputting small current, a step-by-step voltage-regulated DC power supply for electromagnetic detection and emission is proposed.

[0005] In order to achieve the above objectives, the following technical solutions are proposed: A hierarchical voltage-regulated DC power supply for electromagnetic detection and emission, comprising a three-phase power supply, a circuit breaker, a three-phase diode rectifier bridge, an electrolytic capacitor, an H-bridge inverter, a high-frequency transformer, a high-frequency diode rectifier and a DC filter capacitor; The three-phase AC power supply is connected through a circuit breaker, and the three-phase AC voltage of the three-phase AC power supply is converted into a DC voltage through a three-phase diode rectifier bridge, and then the DC voltage is output to the electrolytic capacitor for filtering, thereby reducing the voltage ripple in the DC link; then the filtered DC voltage is converted into a high-frequency AC voltage through an H-bridge inverter; the high-frequency AC voltage passes through the secondary winding of the high-frequency transformer to form an isolated high-frequency AC voltage, and the isolated high-frequency AC voltage is rectified by a high-frequency diode rectifier to form a DC rectified voltage, and then the DC rectified voltage is filtered by a DC filter capacitor to output a DC voltage.

[0006] As a preferred solution, the switch tube in the H-bridge inverter is an IGBT, and the magnitude of the DC voltage is adjusted by adjusting the duty cycle of the IGBT switching time in the H-bridge inverter.

[0007] As a preferred solution, it also includes a sampling circuit, which sets the comparison value of the sampling feedback to within a preset percentage of a given voltage. When the sampling value of the DC voltage is greater than the comparison value, the sampling circuit inputs the difference between the sampling value and the comparison value to the control end for feedback, so as to ensure the stability of the DC voltage output.

[0008] As a preferred solution, it also includes an amplifier circuit. When the DC voltage is output as a low voltage, the difference between the sampling value and the comparison value is amplified by the amplifier circuit and then fed back to the control end. The amplification factor of the amplifier circuit is adjustable. When the voltage is low, the amplification factor is large, and when the voltage is high, the amplification factor is small.

[0009] As a preferred solution, the preset percentage includes 0-20%.

[0010] As a preferred solution, the amplification factor of the amplifier circuit is 5 times.

[0011] As a preferred solution, after the difference is amplified and fed back to the control end, the magnitude of the high voltage DC voltage is adjusted by adjusting the duty cycle of the IGBT switching time in the H-bridge inverter.

[0012] As a preferred solution, the electrolytic capacitor is a high-power electrolytic capacitor.

[0013] As a preferred solution, the high-frequency transformer has three secondary windings, and correspondingly, there are three groups of diode rectifiers; three DC voltages are output, and the three DC voltages are connected in series to form a high-voltage DC voltage.

[0014] Compared with the prior art, the present invention has the beneficial effects of improving the voltage control accuracy when the DC power supply output voltage is low, and improving the stability of the DC power supply control. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a topological structure diagram of the DC power supply in Example 1; Figure 2 is a block diagram of the DC power supply voltage stabilization control in Example 1; Figure 3 This is a block diagram of the DC power supply adjustable gain sampling structure in Example 1. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0017] Example 1 A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission, the topology diagram is as follows: Figure 1As shown, the electromagnetic detection transmitting DC power supply is realized in the form of AC-DC-AC-DC, and the high voltage output is realized by cascading the outputs, such as Figure 1 As shown, the three-phase input is a 380V industrial frequency AC power supply, which is connected to a high-power diode rectifier bridge through a circuit breaker. The output is filtered by a large-capacity electrolytic capacitor to form a DC link, and then connected to a high-power H-bridge inverter consisting of 4 IGBTs to convert the DC voltage into high-frequency (kHz) AC power to power the high-frequency transformer. The secondary side of the high-frequency transformer is composed of three windings, each of which is connected to a single-phase full-bridge high-frequency diode rectifier bridge. The output passes through an electrolytic capacitor to form a DC voltage, and the outputs of the three high-frequency diode rectifier bridges are connected in series to achieve high-voltage output.

[0018] Figure 1 The main parameters are as follows: the three-phase power supply is a generator, the three-phase line voltage is 380V (85%~110%), 50Hz; circuit breaker: three-phase 380V, 300A; diode rectifier bridge, 1200V / 300A; DC bus 540V; H-bridge inverter uses IGBT module, voltage and current parameters are 1200V / 450A; high-frequency transformer ratio is 1:1; high-frequency rectifier diode, voltage and current parameters are 1200V / 300A; output voltage is 0~1500V.

[0019] System control block diagram Figure 2 As shown, the basic idea is to compare the given output voltage with the sampling value of the actual output voltage through the voltage controller, adjust the switching duty cycle of the four IGBTs of the high-power H-bridge inverter, and realize adjustable DC output voltage.

[0020] For the case of a low given voltage, by setting the output voltage sampling signal comparison value, when the output voltage is less than 20% of the given voltage, the sampling signal conditioning circuit is adjusted to increase the amplification ratio by 5 times, thereby ensuring the system accuracy at low voltage output.

[0021] (1) Topology of DC power supply Figure 1 The DC power supply shown is first connected to the three-phase AC power supply through a circuit breaker, and the three-phase AC voltage is converted into DC power through a three-phase diode rectifier bridge, and then filtered by an electrolytic capacitor to reduce the voltage ripple in the DC link; the DC voltage is converted into high-frequency AC power through an H-bridge inverter, and passes through the three secondary windings of a high-frequency transformer to form three isolated high-frequency AC power supplies, which are rectified by high-frequency diodes and filtered by DC filter capacitors before being output in series to form a high-voltage DC power supply.

[0022] (2) Control of DC power supply Figure 2The DC power supply voltage regulation control shown in the figure first sets the output voltage Udc* of the DC power supply, subtracts it from the sampled output voltage Udc through a subtractor, and inputs the error into the voltage controller, outputs the duty cycle d, and then controls the H-bridge inverter of the DC power supply to change the output voltage of the H-bridge inverter, thereby realizing the regulation of the output voltage of the DC power supply.

[0023] (3) DC power supply adjustable gain sampling Figure 3 As shown in the adjustable gain sampling, the DC power supply output voltage Udc is converted into an analog signal through a voltage sensor, and is compared with 20% of the rated voltage Un to control the adjustable gain amplifier to achieve high-multiple amplification at low voltage output. The signal enters the AD acquisition link, and the digital signal is transmitted to the controller to improve the sampling accuracy at low voltage output.

[0024] Specifically, the DC power supply has two working modes: low voltage mode and normal mode. When the power output target value is lower than the set value (for example, 20% of the rated voltage Un), the power supply works in the low voltage mode, and when the power output target value is higher than the set value, the power supply works in the normal mode.

[0025] When the power supply works in low voltage mode, the difference between the sampling value and the comparison value is amplified by the amplifier circuit and then fed back to the control end. The amplification factor of the amplifier circuit is 5 times. By adjusting the duty cycle of the IGBT switching time in the H-bridge inverter, the size of the high voltage DC voltage is adjusted to ensure the stability of the DC voltage output.

[0026] Table 1 Correspondence between output voltage value, amplification factor and duty cycle The DC power supply utilizes switching power supply technology and adopts a high-frequency transformer to effectively improve the system power density, and achieves high-voltage output through a multi-winding transformer to meet the needs of electromagnetic detection.

[0027] The DC power supply is output with regulated voltage through closed-loop control.

[0028] High-precision acquisition of low voltage output is achieved through adjustable gain amplification.

[0029] The above can improve the control accuracy of high voltage DC power supply under low voltage output condition. Finally, it should be noted that the embodiments described in detail above are only the best practices of the invention and cannot be used to limit the scope of rights of the invention. Equivalent replacement of the technical solutions recorded in the aforementioned embodiments does not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the invention, and they should all be included in the scope of the claims and description of the invention.

Claims

1. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission, characterized in that: It includes three-phase power supply, circuit breaker, three-phase diode rectifier bridge, electrolytic capacitor, H-bridge inverter, high-frequency transformer, high-frequency diode rectifier and DC filter capacitor; The three-phase AC power supply is connected through a circuit breaker, and the three-phase AC voltage of the three-phase AC power supply is converted into a DC voltage through a three-phase diode rectifier bridge, and then the DC voltage is output to the electrolytic capacitor for filtering, thereby reducing the voltage ripple in the DC link; then the filtered DC voltage is converted into a high-frequency AC voltage through an H-bridge inverter; the high-frequency AC voltage passes through the secondary winding of the high-frequency transformer to form an isolated high-frequency AC voltage, and the isolated high-frequency AC voltage is rectified by a high-frequency diode rectifier to form a DC rectified voltage, and then the DC rectified voltage is filtered by a DC filter capacitor to output a DC voltage.

2. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in claim 1, characterized in that: The switch tube in the H-bridge inverter is an IGBT. The magnitude of the DC voltage is adjusted by adjusting the duty cycle of the IGBT switching time in the H-bridge inverter.

3. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in claim 2, characterized in that: It also includes a sampling circuit, which sets the comparison value of the sampling feedback to within a preset percentage of a given voltage. When the sampling value of the DC voltage is greater than the comparison value, the sampling circuit inputs the difference between the sampling value and the comparison value to the control end for feedback to ensure the stability of the DC voltage output.

4. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in claim 3, characterized in that: It also includes an amplifier circuit. When the DC voltage is output as a low voltage, the difference between the sampling value and the comparison value is amplified by the amplifier circuit and then fed back to the control end. The amplification factor of the amplifier circuit is adjustable. When the voltage is low, the amplification factor is large, and when the voltage is high, the amplification factor is small.

5. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in claim 3, characterized in that: The preset percentage range is 0-20%.

6. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in claim 5, characterized in that: The amplification factor of the amplifier circuit is 5 times.

7. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in claim 6, characterized in that: After the difference is amplified and fed back to the control end, the magnitude of the high voltage DC voltage is adjusted by adjusting the duty cycle of the IGBT switching time in the H-bridge inverter.

8. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in claim 1, characterized in that: The electrolytic capacitor is a high-power electrolytic capacitor.

9. A step-by-step voltage-regulated DC power supply for electromagnetic detection and emission as claimed in any one of claims 1 to 5, characterized in that: The high-frequency transformer has three secondary windings, and correspondingly, three groups of diode rectifiers; three DC voltages are output, and the three DC voltages are connected in series to form a high-voltage DC voltage.

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